David Anson has created an XPS viewer using the Silverlight 1.1 Alpha.  This app is a very cool idea and really highlights the possibilities of the XAML ecosystem.  David's blog post has more information on how this app was created and he's also posted source.  Hopefully we can fix the downloader crash he found when opening an XPS .zip file before v1 of Silverlight ships this summer.  Click the image below to run the sample.